The present invention relates to an easily replaceable cutter tooth for a circular saw, or any similar rotary machining tool, and to a tool employing the tooth. The tooth is particularly useful on very heavy duty saws used on whole tree harvesters.
In the past decade, automated felling and log bunching equipment has had a major increase in usage where the forest land is of moderate topography. The current popularity of this equipment is due in large part to the productivity gain and cost reduction compared with individual loggers using chain saws. Some of this equipment is capable of harvesting tree stems at rates up to 200 per hour when used under the most favorable conditions. Most mechanical felling equipment operates at much lower rates, however.
One of the popular types of mechanical harvesters in wide use today employs very heavy duty, hydraulically-operated shears to sever the tree from its stump. The use of these shears has resulted in a significant productivity gain, but this has not been without certain cost. Very often severe stresses are induced in the lower part of the tree trunk which later result in splits and/or checking when the tree is processed into lumber.
More recently, harvesters have become available using large, heavy duty circular saws to sever the trees. These have been quite successful in reducing stress damage in the butt portion of the log. However, the saw blades are quite expensive and their maximum life under field conditions has been far below expectations. Prior to the advent of the saw blade described in our earlier U.S. Pat. No. 4,563,929, blade life was generally less than 100 hours before destruction occurred due to accidental contact with a rock or similar object. In addition to the considerable expense of replacing a dull or destroyed blade, installation of a new blade in the field is not a simple matter because the blades are very heavy.
Before the availability of our above-noted saw blade, most of the circular saws available for whole tree felling were simply heavier-duty versions of conventional circular saw blades used in sawmills. These blades either have the teeth formed integrally around the circumference of the saw plate or teeth which can be individually inserted in locations provided around the periphery. In either case, the expensive saw plate itself is readily subject to damage and often is beyond repair when such damage has occurred. The saw described in our U.S. Pat. No. 4,563,929 is an extremely rugged circular saw which is readily field repairable if damaged during use. It comprises a flat, metallic saw plate of circular configuration. The saw plate has a plurality of flat segment members attached around the periphery along each side. Each of these segment members has a plurality of generally buttress-shaped or tooth-shaped, tooth retaining portions located on its outer edge. Segment members on each side of the plate are in an abutting end-to-end relationship. Those segment members on one side of the plate are in a staggered relationship with those on the other side of the plate so that the abutting end portions on one side are generally located opposite the central portions of the similar members on the opposite side. These segments are bolted into relatively softer metal bushings retained in apertures adjacent to periphery of the saw plate. Individual teeth are then bolted to the opposed buttress-shaped portions of the segment members. The saw is particularly strong because the design forms a continuous interconnected ring or hoop around the periphery. Cutting forces are spread throughout the ring and then transmitted to the saw disc. The interconnected hoop is a strong safety feature, since the loss of several bolts in the construction will not cause catastrophic failure of the saw.
We hereby wish to incorporate our earlier U.S. Pat. No. 4,563,929 by reference into the present application. This saw has had considerable acceptance in field use and has been generally very successful in overcoming the problems noted above for its previously available counterparts.